The wiring needs to be fused at the battery, not to protect the amp but to prevent a fire in case of the wire being shorted to ground.

The main wire fuse needs to be sized according to the wire gauge used. If you're running 8awg wire you dont want a fuse larger than about 60A. It doesnt need to match the fuse rating of the amp's internal fuses but shouldnt exceed the current capacity of the wire.